Automotive vehicles are increasingly being equipped with collision warning systems that warn the driver of the vehicle of objects that pose a potential obstruction to the vehicle. Collision warning systems typically include one or more sensors, such as radar sensors and cameras, for sensing the presence of an object in a coverage zone, usually forward or rearward of the host vehicle. While vehicles are typically equipped with side view mirrors for viewing a portion of the side of the host vehicle, it should be appreciated that many vehicles may exhibit an unviewable area which is commonly referred to as a blind spot region. In addition to sensing objects forward and rearward of the vehicle, it is also desirable to sense objects that may be located proximate the side of the host vehicle, particularly in the blind spot region, to warn the driver of any potential obstructions, especially when changing lanes.
A number of detection systems have been proposed for detecting objects in a vehicle blind spot region. Many of the proposed detection systems employ various types of sensors for detecting an object and alerting the driver of the host vehicle of the presence of the object in the blind spot region. One example of a detection system for detecting objects emitting thermal radiation in a blind spot of a vehicle is disclosed in U.S. Pat. No. 6,961,006 and entitled “OBJECT DETECTION FOR A STOPPED VEHICLE,” the entire disclosure of which is hereby incorporated herein by reference. The aforementioned detection approach employs a single thermal detection sensor detecting thermal radiation emitted in a single coverage zone, and detects the presence of an object emitting thermal radiation based on a detected temperature variation when the vehicle is stopped.
Another example of a proposed detection system for detecting objects in a blind spot of a vehicle is disclosed in U.S. Pat. No. 5,668,539 and U.S. Pat. No. 6,753,766, both of which are hereby incorporated herein by reference. The approaches disclosed in the aforementioned patent documents generally employ a plurality of infrared sensors, such as thermopile sensors, to detect changes in a thermal scene along the side of a host vehicle to detect the presence of a thermal emitting object, such as another automobile, in the blind spot region of the host vehicle. These prior techniques employ identical sensors positioned at predetermined locations along the side of the host vehicle, such that the forward-most first sensor is aimed in a particular direction to receive a thermal image from a specific area, and a second sensor is located further aft on the host vehicle and is positioned to generally view the same area, some predetermined time period after the first sensor as the host vehicle moves forward. By knowing speed of the host vehicle, a microcontroller determines the amount of time shift that is necessary to have data from the same physical area at two different points in time. If there is a temperature increase in the second thermal image, then it is assumed to be the heat emitted from a vehicle. The heat could be heat reflected from the road underneath the vehicle or heat generated at the interface of the road and tires of the vehicle.
The thermal radiation detectors disclosed in some conventional detection systems employ multiple thermal detection sensors each having a separate lens element for receiving and detecting thermal energy in a coverage zone. Some techniques employ a thermal detection sensor and a shutter for switching between multiple coverage zones. While these approaches are capable of detecting thermal radiation present in multiple coverage zones, such approaches are often large in size, complex, and expensive. Additionally, some conventional sensing approaches suffer from variations in temperature that exist in the separate lenses and/or an uncontrolled temperature environment of the thermal detection sensors.
It is therefore desirable to provide for a cost-effective and compact thermal radiation detector for detecting thermal radiation in multiple coverage zones. It is further desirable to provide for a multiple zone thermal detection detector that minimizes temperature variations and stray infrared energy to provide a controlled temperature sensing environment.